I'm 175 and run 24 F and 26 R on a short travel (100mm) full-suspension. 40 is sort of high, even at 205. Try this formula:

Rider Weight in pounds divided by 7 = x
x - 1 = Front tire pressure in PSI
x + 2 = Rear tire pressure in PSI
Example: 185lb rider
185/7 = 26.4
Front tire pressure: 26 - 1 = 25 PSI
Rear tire pressure: 26 + 2 = 28 PSI

(Only good for riders 150+, below is too low tire psi)